Hello I would like to paint or coat my rusty exhaust manifolds . Has anyone tried some of the stuff in spray cans available at the parts store thanks in advance 

I power wire Brushed mine using bench Grinder. I used Hi Temp Paint for Headers. Worked for Me. U have to try and get down to bare Cast Iron before painting them.

  

SOURCE - https://www.jet-hot.com/articles/2018/6/29/5-important-reasons-you-should-ceramic-coat-your-exhaust-headers-and-turbo-parts

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After cleaning with wire brushes on a drill. die grinder, pedestal to start and some light sanding, I used Eastwood exhaust paint. Bought the smallest can available and used a brush. They have been on 7 years and still look good. Plenty left too for other cast parts like master cylinders, brake drums, etc.....

56 Vic, B'Ville 200 MPH Club Member, So Cal.